Add ability to pull multiple images without duplication

[wpscholar]

Request from Ben:

I have what I think is a natural extension of the plugin - I'd like the ability to have it pull multiple random posts (without duplication). What would that take?

I mainly imagine a random draw of a deck as needing to be inserted once on a page. Full deck with however many cards drawn.

I suppose allowing multiple shortcodes could help with layout though! As long as it still treated the page load as the event which randomizes the deck and then allows multiple cards to be "pulled" from it.

Thinking further, unless you want to get bugged about layouts, that does probably make the most sense! Treat every shortcode as a single card draw from the deck (deck being a set of posts).